1. Field of the Invention
The present invention relates to a molecular weight controllable, high 1,4-trans polybutadiene catalyst system.
2. Description of the Related Art
Synthesis of 1,4-trans polybutadiene using a butadiene monomer has been reported [Rubber Plast. Age 1963, 44, 42]. 1,4-trans polybutadiene is synthesized by polymerizing a butadiene monomer using a Ziegler-Natta catalyst system including a vanadium compound and alkyl aluminum. However, since the melting point (Tm) of the 1,4-trans polybutadiene is higher than room temperature (70 to 130° C.), the 1,4-trans polybutadiene is required to be aged at high temperature. 1,4-trans polybutadiene may be synthesized using a variety of methods in addition to using the vanadium catalyst system.
Japanese Patent Application No. 1967-67187 discloses synthesis of polybutadiene having a trans content of 75 to 80% using a catalyst combination comprising a cobalt compound, organic aluminum, and phenol.
U.S. Pat. No. 5,089,574 discloses a process for synthesizing 1,4-trans-polybutadiene by polymerizing 1,3-butadiene monomer in the presence of a catalyst system which includes cobalt carboxylate, alkyl phenol, dialkyl sulfoxide, and an organoaluminum compound. In particular, the molecular weight of 1,4-trans polybutadiene is controlled by CS2.
U.S. Pat. No. 5,448,002 discloses a process for synthesizing 1,4-trans-polybutadiene by polymerizing 1,3-butadiene monomer in the presence of a catalyst system which includes cobalt carboxylate, alkyl phenol, dialkyl sulfoxide, and an organoaluminum compound. In particular, the molecular weight of 1,4-trans polybutadiene is controlled using dialkyl sulfoxide.
U.S. Pat. Nos. 6,310,152 and 6,617,406 disclose processes for synthesizing 1,4-trans polybutadiene by polymerizing 1,3-butadiene monomer in the presence of a catalyst system which includes cobalt carboxylate, p-alkyl phenol or a mixture of p-alkyl phenol and o-alkyl phenol, and an organoaluminum compound.
U.S. Pat. No. 5,834,573 discloses a process for synthesizing 1,4-trans polybutadiene by polymerizing 1,3-butadiene monomer in the presence of a catalyst system which includes cobalt (III) acetylacetonate, alkyl phenol, and an organoaluminum compound.
U.S. Pat. Nos. 5,025,059 and 6,608,154 disclose processes for synthesizing trans polybutadiene in the presence of a catalyst system which includes barium thymolate, trialkyl aluminum, and alkyl lithium.
An example of phosphorus-based compounds used for obtaining rubber is described in a literature [Polymer Bulletin, Vol 27, p 41˜46 (1991)]. Ethylene and propylene are copolymerized using (TiCl4+MgCl2)-phosphate catalyst and (TiCl3+MgCl)-phosphate catalyst to obtain rubber with low crystallinity.
According to U.S. Pat. Nos. 6,545,107, 1,2-polybutadiene having vinyl groups and a yield ranging from 80 to 90% is synthesized using a catalyst including a molybdenum-containing compound, a silyl phosphonate compound, and an organoaluminum compound.
According to European Patent No. 1770128 A1, discoloration of 1,2-polybutadiene is compared by applying a phosphorus-based compound, a phenol-based compound, and a sulfur-containing ether compound, in the preparation of 1,2-polybutadiene using a cobalt catalyst. U.S. Pat. No. 5,109,082 discloses a process for producing 1,4-cis polybutadiene using a catalyst system including cobalt octoate and diethylaluminum chloride in which a trialkyl phosphate compound is used as a gelation inhibitor.
Since conventionally prepared trans polybutadiene has a large molecular weight and its molecular weight is not controllable, the Mooney viscosity of its compound is too high to be processed during rubber processing.